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13.2. Goal Seek Tool
Use Goal Seek Tool to search for a value of a single model variable that yields a given desired value of another single variable. For example, you can use the Goal Seek to find the break-even value for sales (the break-even is the amount of sales whose marginal revenue just covers the fixed costs and the profit is thus zero).
13.2.1. Using the Tool
First, select the ``Goal Seek...'' tool item from ``Tools'' menu. Specify the output variable cell (``Set Cell'') by typing the cell reference into the entry or by clicking the worksheet cell. If you are searching for the break-even point, for example, you should specify the cell reference of the profit calculation here.
Specify the desired result for the output variable cell into the ``To Value'' cell. In the search for the break-even, specify this to be zero.
Specify the input variable cell (``By changing cell'') by typing the cell reference into the entry or by clicking the worksheet cell. In the search for the break-even, specify the cell reference of the sales here. When you have done this, you may want to press the ``Apply'' button to start the tool.
13.2.2. Results
Gnumeric will systematically iterate the model by changing the input value to achieve the desired result, if possible. If goal seek was successful the tool displays the message ``Goal Seeking with cell __ found a solution''.
It is possible that Gnumeric does not find a solution that generates the desired result. There may not be such a solution for the model, or, it may be too difficult to find. For example, the mathematical function behind the calculation may have many non-continuous points.
13.2.3. Desired Value in a Given Range
If Gnumeric did not find a solution that generates the desired result, you may want to try to specify a range (minimum and maximum) in which the value of the output variable should be. To do this, specify the ``Minimum'' and ``Maximum'' entries.